The overall objectives of the proposed research are to define further: the reaction mechanisms in the generation and release of the chemical mediators, primary and secondary, of immediate hypersensitivity utilizing both human and rat mast cell-enriched systems; the chemical structure and function of primary mast cell-derived mediators with chemotactic, enzymatic, and regulatory functions as well as the secondary mediators; the physicochemical and functional characteristics of the kinin-generating and fibrinolytic systems with particular emphasis on those originating in tissues; the immunochemistry and immunobiology of the alternative complement pathway and the dual recognition of activators by separate humoral and cellular mechanisms; and the characterization of selected biochemical systems of neutrophils and eosinophils which appear to afford special functions.